The present invention relates to a novel scratch ink composition and a writing utensil utilizing the composition.
The scratch ink is a kind of ink adapted to form an opaque film capable of hiding the character, numeral, symbol and/or other pattern image on a substrate for use in the field of lottery and game tickets or the like and removable by scratching with a coin edge, a fingernail or a rubber eraser.
With regard to the printed matter embodying such a function, there is known the artifact produced by forming a desired image, such as a drawing, characters, figures or a photograph, by printing on the surface of a substrate, such as a paper or plastic sheet, applying a wax-formulated solution of a medium composed of a resin, a vegetable oil, a petroleum-based solvent and a desiccant over the image area to form a medium layer, and forming an opaque image (layer) capable of hiding the first-mentioned image by printing over said medium layer either locally or all over so that when the surface of the artifact is abraded or scratched the printing ink forming said opaque image is dislodged to reveal the underlying printed image (Japanese Examined Utility Model Publication S44-12094).
However, to produce such a printed matter, it is necessary to form a medium layer on the printed character, figure or the like image in the first place and then form an opaque layer, so that the method can hardly be said to be expedient. Particularly because it is intended for the production of printed matter, the method is unsuited for gimmicks to be enjoyed personally or at the family level.
There also is known an ink composition compatible with paper such that the characters or pattern written on a paper substrate can be erased with a rubber eraser or the like characterized by its comprising a uniform pigment dispersion prepared by dispersing a pigment selected from the group consisting of carbon black and aniline black in an aqueous medium containing a high molecular polyethylene oxide, optionally with the aid of a surfactant, and containing 1xcx9c20 weight % of said pigment and 0.01xcx9c5 weight % of said high molecular polyethylene oxide (Japanese Examined Patent Publication H1-39470).
However, the film formed from this ink composition is hardly removable with a rubber eraser or the like at times and the composition remains to be further improved in erasability.
There also is available an erasable ink characterized by its comprising a resin having a film-forming temperature of not higher than 0xc2x0 C. or a glass transition temperature of not higher than 0xc2x0 C., a colored powder consisting of fine spherical particles ranging from 1 to 20xcexc in diameter, and water and having an ink viscosity of 5xcx9c35 mPaxc2x7sec (Japanese Unexamined Patent Publication H5-279614).
Though this ink is erasable, it inherently has no covering power so that characters or other patterns cannot be hidden. Therefore, the ink cannot be used as a scratch ink which is intrinsically expected to hide character, pattern or other images. On the other hand, if an attempt is made to impart a covering power to this ink, chances are that its erasability will be sacrificed.
Thus, these known inks are invariably deficient in one or more of the performance quality parameters of erasability, hiding power and ease of use, and up to the present there has not been available an ink satisfying all the requirements, that is to say an ink suited for erasable applications.
An object of the present invention is to provide a scratch ink composition improved in erasability, hiding power and ease of use.
After an intensive research to overcome the above disadvantages of the prior art, the present inventor found that an ink composition having the herein-defined composition accomplishes the above object and has accordingly developed the present invention.
The present invention, therefore, is directed to the following scratch ink compositions and a writing utensil which utilizes the same.
1. A scratch ink composition comprising a flaky pigment, a resin component and a solvent, the particles of the pigment having a particle size distribution (as determined with a laser diffraction particle size analyzer) such that the integral fraction of particles not larger than 10 xcexcm in diameter is not more than 30%.
2. A scratch ink composition as defined in the above paragraph 1 wherein the particles constituting an integral fraction of 30% in particle size distribution (as determined with a laser diffraction particle size analyzer) are 3xcx9c200 xcexcm in diameter and that its thickness is {fraction (1/40)}xcx9c{fraction (1/60)} of the particle diameter.
3. A writing utensil comprising the composition defined in the above paragraph 1 or 2 as its ink component.
4. A scratch material comprising a film formed from the composition defined in the above paragraph 1 or 2 on a substrate carrying a character or pattern image, said film hiding said character or pattern image.
5. A method of producing a scratch material which comprises printing a substrate with a character or pattern image and then applying the composition defined in the above paragraph 1 or 2 in superimposition to hide said character or pattern image.
1. Scratch Ink Composition
Referring, first, to the flaky pigment for use in the composition of the present invention, its particle size distribution (as determined with a laser diffraction particle size analyzer) should be such that the integral fraction of particles not larger than 10 xcexcm is not more than 30% (preferably not more than 20%). Inasmuch as this condition is satisfied, any commercial pigment can be used as it is.
Even the pigment which fails to satisfy the above condition can be used as the pigment in the present invention by eliminating or reducing the proportion of particles not larger than 10 xcexcm by the known fractionation technique such as centrifugation, filtration or addition of a flocculant or, where necessary, adding particles over 10 xcexcm in diameter.
The particle morphology of the flaky pigment is not particularly restricted inasmuch as the desired hiding power can be attained but may usually be such that the particle diameter (referred to also as D30) corresponding to an integral fraction of 30% (D30) in particle size distribution (as determined with a laser diffraction particle size distribution analyzer) is about 3xcx9c200 xcexcm, preferably 15xcx9c50 xcexcm. Moreover, the thickness of the flaky pigment may be {fraction (1/40)}xcx9c{fraction (1/60)}, preferably about {fraction (1/50)}, of the D30 value.
The flaky pigment (raw material) is not restricted inasmuch as it provides the desired hiding power and may be an organic pigment or an inorganic pigment (inclusive of a metal powder pigment). For example, an aluminum powder pigment or a metal-coated inorganic pigment (e.g. the pigment obtained by covering glass flakes with a metallic film by a suitable coating technique such as electroless plating or sputtering; the pigment obtained by covering an inorganic or metallic material, e.g. mica or aluminum, with a metallic film by a suitable coating technique; etc.) can be mentioned. These pigments can be used independently or in a suitable combination.
As the flaky pigment, commercial products can also be used. To mention a few examples, the aluminum powder pigment includes xe2x80x9cAlpaste WXM-U75Cxe2x80x9d, xe2x80x9cAlpaste WXM5422xe2x80x9d and xe2x80x9cAlpaste WXM1440xe2x80x9d (all from Toyo Aluminum Co.); the pigment obtained by covering glass flakes with a metallic film by electroless plating (metal-coated inorganic pigment) includes xe2x80x9cMetashine REFSX-2015PSxe2x80x9d, xe2x80x9cMetashine REFSX-2025Pxe2x80x9d and xe2x80x9cMetashine REFSX-2040PSxe2x80x9d (all from Toyo Aluminum Co.); and the pigment obtained by covering glass flakes with a metallic film by sputtering (metal-coated inorganic pigment) includes xe2x80x9cCrystal Color GF2125xe2x80x9d, xe2x80x9cCrystal Color GF2525xe2x80x9d, xe2x80x9cCrystal Color GF2140xe2x80x9d and xe2x80x9cCrystal Color GF2125xe2x80x9d (all from Toyo Aluminum Co.).
The proportion of flaky pigment (on a solid basis) can be judiciously selected according to its kind and may be generally about 3xcx9c30 weight %, preferably 4xcx9c15 weight %, based on the total composition of the present invention. When the proportion of the flaky pigment is too small, a sufficient hiding power may not be obtained. When it is excessive, the increased solid content tends to lower the fluidity of the composition.
The resin component is not particularly restricted inasmuch as it can be used for viscosity adjustment of the ink composition and is capable of forming an opaque film over a written or printed image, thus including water-soluble resins and oil-soluble resins. As such water-soluble resins, there can be mentioned microbial secretion polysaccharides such as pullulan, xanthan gum, welan gum, rhamsan gum, succinoglucan, etc.; plant-derived water-soluble polysaccharides or derivatives thereof, such as guar gum, locust bean gum, pectin, etc.; animal-derived water-soluble polysaccharides or proteins and derivatives thereof, such as gelatin, casein, etc.; cellulose derivatives such as hydroxyethylcellulose, carboxymethylcellulose (CMC), etc.; cyclodextrins and derivatives thereof, such as xcex1-cyclodextrin, xcex2-cyclodextrin, xcex3-cyclodextrin, and methyl or other derivatives thereof; soybean-derived water-soluble polysaccharides or derivatives thereof which are available from commercial sources under the tradenames of e.g. xe2x80x9cSoya Five S-DNxe2x80x9d, xe2x80x9cSoya Five S-LNxe2x80x9d, xe2x80x9cSoya Five S-LN1xe2x80x9d, xe2x80x9cSoya Five S-DA100xe2x80x9d and xe2x80x9cSoya Five S-LA200xe2x80x9d (all from Fuji Oil Company); and synthetic water-soluble resins such as acrylic resin, styrene-acrylic resin, styrenic resin, maleic acid resin, styrene-maleic acid resin, polyvinylpyrrolidone, urethane resin, polyvinyl alcohol (PVA) and so on. The oil-soluble resins are not particularly restricted, either, inasmuch as they are soluble in the solvent component of the composition of the present invention, thus including ketonic resins, phenolic resins and xylenic resins, among others. These resins can be used independently or in a combination of 2 or more species.
Among these resin components, the water-soluble resin is preferably a resin containing a microbial secretion polysaccharide or a derivative thereof as an essential component (particularly a resin comprising a microbial secretion polysaccharide or a derivative thereof and PVA). The microbial secretion (metabolite) polysaccharide inclusive of their derivatives are preferred because they impart thixotropy to the ink and provide for improved writing quality. The preferred species of said oil-soluble resin is a resin system comprising at least one member selected from the group consisting of ketonic resin, phenolic resin and xylenic resin.
The proportion of the resin component can be judiciously selected according to the kind of resin, the kind of solvent, etc. and may for example be generally about 0.01xcx9c30 weight %, preferably 0.3xcx9c20 weight %, based on the total composition of the present invention. When the resin content is too high, the increased viscosity tends to detract from writing or printing quality. When the resin content is too low, the flaky pigment tends to be precipitated.
The solvent is not particularly restricted but may be any solvent that is generally used. Thus, for example, water, alcohols such as methanol, ethanol, propanol, butanol, etc.; glycols such as ethylene glycol, diethylene glycol, propylene glycol, etc.; glycol ethers such as ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and carbitols such as diethylene glycol monomethyl ether can be mentioned. Furthermore, glycerin, trimethylolpropane, etc. can also be employed. Among these, water, aliphatic alcohols containing 1xcx9c4 carbon atoms, propylene glycol monomethyl ether and glycerin are preferred. These solvents can be used independently or two or more of them can be used in a suitable combination.
The proportion of the solvent can be judiciously selected according to the kind of flaky pigment used and may for example be generally about 50xcx9c90 weight %, preferably 60xcx9c90 weight %, based on the total composition of the present invention. When the amount of the solvent is too large, the concentration (density) of the written or printed image tends to be insufficient. Conversely when the amount of the solvent is too small, the dispersibility or solubility of the colorant, for instance, tends to be inadequate.
In addition to the above components, the composition of the present invention may be optionally supplemented with various known additives such as the colorant, lubricant, corrosion inhibitor, preservative/antifungal agent, dye solubilizer, surfactant and so on.
Particularly as the colorant, known organic and inorganic pigments and dyes other than said flaky pigment can be selectively formulated in a suitable proportion. As such other pigments, there can be mentioned phthalocyanine, quinacridone, carbon, etc., and as said other dyes, various dies in such series as the triphenylmethane, xanthene, anthraquinone, metal complex, and copper(II) phthalocyanine series can be employed. Aside from these, fluorescent pigments, phosphorescent pigments, colored emulsions, etc. can also be employed.
When an organic or inorganic pigment is used in the present invention, it can be used in the form of a dispersion in water. In this case, for enhancing aqueous dispersibility, a pigment-dispersant resin such as a styrene-acrylic copolymer may be formulated. In addition, where necessary, a pH control agent such as triethanolamine can be added.
The formulating amount of the colorant can be judiciously selected according to the kind of colorant, among other factors, but may for example be about 0.05xcx9c10 weight %, preferably 1xcx9c10 weight %, based on the total composition of the invention. When said aqueous pigment dispersion is used as the colorant, the formulating calculation should be based on the sum of the amounts of the pigment and dispersant resin used (pigment base).
The composition of the present invention can be produced by blending the above respective components and following the known dispersing procedure. When a water-soluble resin, for instance, is used as the resin component, the production process may comprise mix-dispersing the solvent and flaky pigment, optionally together with the colorant, adding the water-soluble resin to the dispersion, filtering the mixture and degassing the filtrate. When an oil-soluble resin is used as the resin component, the production process may comprise mix-dispersing the solvent and oil-soluble resin, optionally together with the colorant, stirring the mixture under heating at a suitable temperature, returning the resulting solution to room temperature, adding the flaky pigment, filtering the mixture and degassing the filtrate.
2. Writing Utensil
The composition of the present invention can be used in substantially all applications, for example as a printing ink or as the ink component of a writing utensil. The writing utensil includes ball-point pens, markers and so on. Except that the composition of the present invention is used as the ink component, such writing utensils may otherwise have known structures.
3. Scratch Material
The present invention encompasses a scratch material characterized by its comprising a film formed from the composition of the invention on a substrate carrying a character or pattern image expressed thereon and hiding said character or pattern image.
The substrate mentioned above is not particularly restricted inasmuch a film such as described above can be formed thereon, thus including various kinds of paper, wooden/fibrous substrates, resin substrates, metal substrates, ceramic substrates, glass substrates and composite artifacts thereof. In the present invention, paper can be used with advantage. The morphology of the substrate is not particularly restricted but may for example be a sheet or a sphere.
The thickness of said film is not particularly restricted inasmuch as the underlying character or pattern image can be hidden. Usually, the film thickness may be about 5xcx9c50 xcexcm. The coating film of the scratch material of the present invention principally comprises the very film formed from the composition of the invention and it is preferable that no other coating film be involved.
The character or pattern image in the present invention includes all expressions such as figures, symbols, pictures, motifs, and so on. Moreover, the character or pattern image may have been hand-written or printed. The printing technology which can be used is not particularly restricted.
The scratch material of the present invention can be produced by a process which may for example comprise applying a character or pattern image on a substrate by printing and, then, coating the printed substrate with the composition of the present invention so as to hide said character or pattern image. The printing technology and coating technology which can be used here are not particularly restricted, either, but may respectively be the one known in the art.
In accordance with the present invention, a scratch ink composition which is very satisfactory in erasability, hiding power and ease of use can be provided.
While the composition of the present invention is capable of hiding the character or pattern image recorded on a substrate more or less completely, the image (coating film) formed with the composition of the invention can be easily removed by scratching or abrading with a fingernail, a coin edge, a rubber eraser or the like to thereby reveal and enables identification of the character or pattern image recorded on the substrate. Thus, with the composition of the present invention, a scratch material with an excellent scratch performance can be manufactured.
Furthermore, the composition of the present invention can be used not only as a printing ink but also as the ink component of a writing utensil. In addition, a scratch effect can be obtained simply by applying the composition on the existing printed matter, so that it can be used personally or at the family level, not being restricted to use in the field of business, with greater convenience than the conventional printing ink.